fix: add metaTxApiId property to PreMintButton

[levalleux-ludo]

Description

Added metaTxApiId optional property to PreMintButton component to enable custom Biconomy API ID configuration for meta-transactions.

Changes:

• Added metaTxApiId?: string to component props and type definitions (lines 24, 28, 47)
• Passed metaTxApiId to relayBiconomyMetaTransaction via metaTxConfig.apiId override (lines 84-86)

This allows consumers to specify a different Biconomy API ID per button instance when the default configuration is insufficient.

How to test

import { PreMintButton } from "@bosonprotocol/react-kit";

// Use custom Biconomy API ID for meta-transaction
<PreMintButton
  offerId="123"
  amount={5}
  metaTxApiId="custom-api-id-here"
  onSuccess={(receipt) => console.log("Success", receipt)}
/>

Verify the custom API ID is used in the Biconomy relay call when meta-transactions are enabled.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.98%. Comparing base (7188cf3) to head (9b53ee7).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #988      +/-   ##
==========================================
+ Coverage   86.39%   90.98%   +4.58%     
==========================================
  Files         167      176       +9     
  Lines        7095     7190      +95     
  Branches     1299     1322      +23     
==========================================
+ Hits         6130     6542     +412     
+ Misses        965      648     -317     

Flag	Coverage Δ
common	92.59% <ø> (?)
core-sdk	56.41% <ø> (?)
e2e	86.08% <ø> (+<0.01%)	⬆️
eth-connect-sdk	95.06% <ø> (?)
ethers-sdk	74.45% <ø> (?)
ipfs-storage	91.75% <ø> (ø)
metadata	94.70% <ø> (ø)
unittests	60.76% <ø> (-32.87%)	⬇️

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[levalleux-ludo]

@copilot

[Copilot]

@levalleux-ludo I've opened a new pull request, #991, to work on those changes. Once the pull request is ready, I'll request review from you.

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